Northwest Fisheries Science Center

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Document Type: Report
Center: NWFSC
Document ID: 8473
Title: Impacts of climate change on salmon of the Pacific Northwest: a review of the scientific literature published in 2014
Author/Editor: Lisa G. Crozier
Year: 2015
Institution: National Marine Fisheries Service, Northwest Fisheries Science Center. Seattle, Washington

Observations of Climate in 2014

            The most important observations of recent climate trends reveal that 2014 was the hottest year on record globally, terrestrially, and in the ocean (Blunden and Arndt 2015).  The California Current shifted from a highly productive La Niña state in 2013 to a less productive, anomalously warm state by fall 2014, with striking warmocean anomalies in some areas (Leising et al. 2014).  The ¿2014 warm anomaly¿ or ¿the blob¿ (Bond et al. 2015) consisted of an unusually large area of warm sea surface temperatures that expanded from the Gulf of Alaska in winter to the Pacific coast in summer 2014.  Numerous unusual biological sightings indicated a year of marked climate anomalies.   

            At the global level, careful attention has been devoted to attribution of temperature trends to natural variability vs. increasing anthropogenic input of CO2, and a wide consensus has emerged that the latter is necessary to explain recent observations.  However, attribution is notoriously difficult at the regional level, where natural variability plays a much larger role.  Numerous retrospective analyses at all spatial scales have documented rising ocean temperatures.  Nevertheless, a provocative analysis (Johnstone and Mantua 2014a) found that the long-term trend in sea surface temperature in the northeast Pacific is likely driven mostly by natural variability in winds.  These authors did not deny that ongoing increases in CO2 will raise sea surface temperatures in the future.  Rather, they emphasized that natural variability extends beyond decadal patterns to include lowfrequency phenomena that we cannot fully understand or predict, such as the observed trend in winds over the Pacific.

            Similarly, in California over half of the state was classified as being in ¿extraordinary drought¿ status, yet the highpressure phenomenon driving this 3year drought appears largely due to natural variability in atmosphere-ocean dynamics (Seager et al. 2014).  However, the high temperatures that exacerbated this drought are likely to have been influenced by anthropogenic factors (Funk et al. 2014; Swain et al. 2014; Wang and Schubert 2014).  

            Biological evidence of impaired shell production due to ocean acidification is accompanied by several studies that document continued declines in ocean pH (Bednarsek et al. 2014; Busch et al. 2014).  Oceanographic models continue to improve our understanding of upwelling (Jacox et al. 2014), how upwelling influences ocean acidification (Lachkar 2014), and how rising global temperatures affect both upwelling (Sydeman et al. 2014a) and climate oscillations such as the El Niño Southern Oscillation (ENSO, Ohba et al. 2014). 

Recent Behavioral Changes in Salmon

            Several observations have documented behavioral shifts in salmon that are likely due to warming climate trends over the past half century.  In fall Chinook salmon from the Hanford Reach of the Columbia River, spawn date has shifted one week later since 1950, during a 2°C period of warming (

  • Crozier.2015-BiOp-Lit-Rev-Salmon-Climate-2014.pdf 201K, uploaded 07/31/2017
  • Theme: Recovery and rebuilding of marine and coastal species
    Foci: Describe the relationships between human activities and species recovery, rebuilding and sustainability.